1. Field of the Invention
The present invention relates to a scroll compressor, and more particularly, to a coupling structure of an eccentric bush of a scroll compressor capable of preventing damage to the eccentric bush or a rotary shaft by dispersing the power applied to the rotary shaft and the eccentric bush during the operation of the compressor.
2. Description of the Background Art
In general, a compressor converts electric energy into kinetic energy, and compresses a refrigerant by the kinetic energy. The compressor is the kernel of a freezing cycle system. According to a compression mechanism for compressing a refrigerant gas, there are various kinds of compressors such as a rotary compressor, a scroll compressor, a reciprocal compressor and the like. Such compressors are used in a refrigerator, an air conditioner, a showcase and the like.
FIG. 1 is a cross-sectional view illustrating one embodiment of the scroll compressor.
As shown therein, the scroll compressor includes: a casing 10 provided with a suction pipe 11 and a discharge pipe 12; a main frame 20 and a sub-frame 30 fixedly coupled to the upper and lower portions inside the casing 10, respectively, with a certain interval; a fixed scroll 40 fixedly coupled to the casing 10 so as to be positioned at an upper side of the main frame 20; an orbiting scroll 50 positioned between the fixed scroll 40 and the main frame 20 so as to be orbitably interlocked with the fixed scroll 40; an Oldham ring 60 positioned between the fixed scroll 40 and the main frame 20, for preventing a self-rotation of the orbiting scroll 50; a driving motor (M) fixedly coupled to the casing 10 so as to be positioned between the main frame 20 and the sub-frame 30, for generating a driving force; a rotary shaft 70 for transferring the driving force of the driving motor (M) to the orbiting scroll 50; and a valve assembly 80 mounted on an upper surface of the fixed scroll 40.
The main frame 20 includes: a shaft insertion hole 22 formed at a frame body portion 21 of predetermined shape, into which the rotary shaft 70 is penetratingly inserted into; a boss insertion groove 23 communicating with the shaft insertion hole 22 having an inner diameter greater than that of the shaft insertion hole 22; and a bearing surface 24 formed at an upper surface of the frame body portion 21, by which the orbiting scroll 50 is supported.
The fixed scroll 40 includes: a body portion 41 having a predetermined shape; a wrap 42 formed in an involute curve shape of predetermined thickness and height at one surface of the body portion 41; a discharge hole 43 penetratingly formed at the center portion of the body portion 41; and a suction hole 44 formed at one side of the body portion 41.
The orbiting scroll 50 includes: a circular plate part 51 having certain thickness and area; a wrap 52 formed in an involute curve shape of certain thickness and height at one side of the circular plate part 51; a boss part 53 penetratingly formed at the center portion of the other side of the circular plate part 51 to a certain height; and a shaft insertion groove 54 formed inside the boss part 53 to a certain depth, into which part of the rotary shaft 70 is inserted. The orbiting scroll 50 is coupled between the fixed scroll 40 and the main frame 20 such that the wrap 52 of the orbiting scroll 50 is interlocked with the wrap 42 of the fixed scroll, the boss part 53 is inserted into the boss insertion groove 23 of the main frame 20, and one surface of the circular plate part 51 is supported by the bearing surface 24 of the main frame.
The rotary shaft 70 includes: a shaft part 71 having a certain length; an eccentric part 72 extending from one side of the shaft part 71 to a certain length so as to be eccentric from the center of the shaft part 71; and an oil path 73 penetratingly formed at the shaft part 71 and the eccentric part 72.
As for the rotary shaft 70, the shaft part 71 is coupled with the driving motor (M). One side of the shaft part 71 of the rotary shaft 70 is penetratingly inserted into the shaft insertion hole 22 of the main frame and the eccentric part 72 is inserted into the shaft insertion groove 54 of the orbiting scroll.
Then, an eccentric bush 90 in a predetermined shape is inserted into the eccentric part 72 of the rotary shaft, and a fixed bush 100 slidingly contacting the eccentric bush 90 is fixedly coupled with an inner wall of the shaft insertion groove 54 of the orbiting scroll.
The oil is filled at the lower part of the casing 10.
Undescribed reference numerals 110, 120, 130, 140 and 150 are a stator, a rotor, a balance weight, an oil feeder and a high and low pressure separator, respectively.
An operation of the scroll compressor having such a construction will be described as follows.
If the power is applied to the scroll compressor, rotary power is generated from the driving motor (M) by the operation of the driving motor (M), and the rotary power of the driving motor (M) is transferred to the orbiting scroll 50 through the rotary shaft 70. As the rotary power of the rotary shaft 70 is transferred to the orbiting scroll 50, the orbiting scroll 50 coupled to the eccentric part 72 of the rotary shaft 70 orbits on the basis of a central axis of the rotary shaft 70. Prevented from its self-rotation by means of the Oldham ring 60, the orbiting scroll 50 orbits.
As the orbiting scroll 50 orbits, the wrap 52 of the orbiting scroll is interlocked with the wrap 42 of the fixed scroll. By the orbiting movement of the orbiting scroll, a plurality of compression pockets (P) formed by the wrap 52 of the orbiting scroll and the wrap 42 of the fixed scroll are moved into the center portion of the fixed scroll 40 and the orbiting scroll 50 and gradually contracted in volume.
The compression pockets suck, compress and discharge the gas through the discharge hole 43 of the fixed scroll.
The oil filled in the lower part of the casing 10 flows via the oil path 73 of the rotary shaft by the rotation of the rotary shaft 70 and is supplied to components where a sliding motion is generated.
Meanwhile, by the rotation of the rotary shaft 70, the eccentric part 72 of the rotary shaft moves in a circular motion by taking a distance eccentric from the center of the shaft part 71 of the rotary shaft as a rotating radius and the circular motion of the eccentric part 72 of the rotary shaft is transferred to the boss part 53 of the orbiting scroll, whereby the orbiting scroll 50 orbits. In addition, the eccentric bush 90 inserted into the eccentric part 72 not only prevents direct friction between the eccentric part 72 of the rotary shaft and the boss part 53 of the orbiting scroll but also keeps the rotation of the rotary shaft 70 stable.
FIG. 2 is a plan view showing a coupling structure of the conventional eccentric bush.
As shown therein, the coupling structure of the eccentric bush is as follows.
The eccentric part 72 of the rotary shaft is constructed in such a manner that a cutting plane (F1) cut to have a certain plane is formed at one outer circumferential surface of a cylindrical shape with certain length and outer diameter. The center of the eccentric part 72 is eccentric from the center of the shaft part 71 with a certain distance.
The eccentric bush 90 includes a cylindrical body portion with certain length and outer diameter and an insertion hole 92 penetrated into the cylindrical body portion 91 in a longitudinal direction. The insertion hole 92 has an inner diameter corresponding to an outer diameter of the eccentric part 72, and has a plane portion (F2) having a certain width at its one inner circumferential surface. The center of the insertion hole 92 is positioned to be eccentric from that of the cylindrical body portion 91 with a certain distance. The area of the plane portion (F2) of the eccentric bush 90 is smaller than that of the cutting plane (F1) formed at the outer circumferential surface of the eccentric part of the rotary shaft.
The eccentric bush 90 is coupled with the rotary shaft 70 such that the eccentric part 72 is inserted into the insertion hole 92. The plane portion (F2) formed at one inner circumferential surface of insertion hole 92 of the eccentric bush and the cutting plane (F1) of the eccentric part maintain a predetermined interval therebetween, through which the oil is supplied.
In addition, the eccentric bush 90 coupled to the eccentric part 72 of the rotary shaft is inserted into the shaft insertion groove 54 formed at the boss part 53 of the orbiting scroll.
If rotary power of the driving motor (M) is transferred to the rotary shaft 70 and thus the shaft part 71 of the rotary shaft rotates, the eccentric part 72 of the rotary shaft moves in a circular motion and the circular motion of the eccentric part 72 is transferred to the orbiting scroll 50 through the eccentric bush 90, whereby the orbiting scroll 50 orbits.
However, in the coupling structure of the eccentric bush, as shown in FIG. 3, when the compressor operates or is stopped, the edge of the cutting plane (F1) of the eccentric part of the rotary shaft comes in contact with and bumps against the plane portion (F2) of the eccentric bush. As the eccentric part 72 of the rotary shaft bumps against the eccentric bush 90 repetitively, a crack is generated on the eccentric bush 90 since concentrated stress is repetitively applied to a specific portion of the eccentric bush 90 of relatively low intensity. The eccentric bush 90 is damaged in certain circumstances.